After seeing the post with the implemented feedback, I thought it would be good to finally finish the post I was preparing in the same structure of my Spain proposal. I hope you are still looking at feedback here! In the next post I'll address the map after the changes you implemented (which covers like half of the things suggested here! incredible work!)
Friesland
A: Sneek over Makkum
As mentioned by many people, Makkum wasn't a city in this period, and Sneek was far more important than Makkum. Stavoren is also in the area and is the oldest Frisian city, but it had heavily declined by the late Middle ages, making Sneek the better choice. Makkum was an important industrial centre later in the period however - and did have important seashell fishing, so your original tradegood of Pearls made sense here, there was no need to remove it.
1. Wolvega
Between Friesland (where it is today) and Overijsel, the region of Stellingwerven was de jure governed by Utrecht but was in practice an independent peasant state for a long time, including in 1337. Despite the lack of major cities, I believe this is worth representing due to its size and unique situation - and the city of Heerenveen, today one of the largest in the province, was eventually founded here. The tradegood, as expected from such an agricultural area, would be Wheat, though it's peat production could also be represented by Livestock
2. Winsum
As others have stated, Groningen should be an independent city in this period. It's location should thus be small and landlocked- the Frisian region of Hunsigo and smaller regions to its west are instead covered by Winsum. Winsum was a developed market town, but it was completely overshadowed by its rival of Groningen. Mostly produced barley, so Sturdy Grains are a good tradegood
3. Winschotten
Wedde and the region of Westerwolde should be landlocked and owned by the bishopric of Munster at this time - to keep Frisia connected and represent the Oldambt region, I would add Winschotten. While it only received city rights in the early 19th century, it was a notable settlement. The location would also include Midwolda, which was the most important settlement earlier in the middle ages. Another agricultural area, Wheat fits well.
While I'm mostly keeping ideas for Germany for its own map week, I'm including East Frisia as well given its political situation at the time.
4. Weener
Representing the parts of East Frisia west of the river Ems (Rheiderland). This region was always far more connected to Ommeland in the Netherlands than the rest of German East Frisia, and kept a degree of administrative separation until 1600.
5. Aurich
Aurich is the biggest city in inland East Frisia and the second largest after Emden. It was the supposed seat of the Frisian assembly as well. If you want to add less locations, just replacing Wittmund with Aurich works as well, however I'd keep them separate as Harlingerland stayed independent from thr Counts of East Frisia for a long time
6. Jever
The most important omission in East Frisia atm, Jever maintained its independence as a separate lordship for a long time, was a city and an important trading centre and later an exclave of the faraway lords of Anhalt, and most famously, Russia (!). Jever is best known for its beer so whatever is best to represent Hops (Sturdy Grains?) is the best tradegood. This would also represent the borders of Oldenburg better for much of the early period of the game, as they acquire Varel much before Jever. Eventually, Wilhelmshafen is founded in this location and surpasses Jever
Overijssel and Gelre
A: Coevorden over Emmen, Meppel over Coevorden
As people have mentioned before, Coevorden was the only actual city in Drenthe for a long time, but it declined with time and was replaced by Emmen (only by the 19th/20th century though). Meppel is the better option to cover the western parts of the province, as it has been a city since 1644.
1. Kampen
Kampen was the largest city in Northern Netherlands for much of the period, until decline in the 17th century. Most of the city's income came from maritime trade and leasing of poldered land, so the raw tradegood is hard to find, perhaps Fish or Sand? Regardless, it's an excellent option to represent the rural Overijssel
The borders of Enschede should be adjusted to match the borders of the region of Twente, shrinking Deventer. This does make the location quite large, so...
2. Oldenzaal
Covering the cities of Oldenzaal (which was briefly a Spanish exclave while the rest of Oldenzaal was free) and Almelo (which had a separate county). Oldenzaal was the most important city in Twente for most of the period, so it could be a good replacement for Enschede if not added as well. Wheat seems to fit well as a tradegood.
3. Urk
You mention that you (correctly) sank Flevoland as it's a 20th century creation. However, not ALL of Flevoland was underwater. The town of Urk used to be an island, the only part of the province to exist in the game period, alongside some smaller islands. This made Urk quite isolated from the rest of Dutch culture, which continues even to this day. Politically it was still an independent lordship in 1337, and would fall vassal to Utrecht and Holland later. The main issue here is the small size of the islands before land reclamation - but the Dutch coast is already a big compromise. Fish is the only logical tradegood as the town lived off Fishing
4. Tiel
Betuwe was a rather rich and populous area, and Tiel is one of the oldest cities in the Netherlands and a trade centre throughout the period. The area was also contested between Gelre and Brabant at the start. The tradegood would naturally be Fruit, as already suggested before
B: The borders of the locations in Gelre are seriously redrawn
- Doetinchem is redrawn to represent the baronies of Bergh, Wisch, Bredevoort and Borculo. Zutphen covers the rest of the quarter.
Arnhem is redrawn to be smaller and closer to Germany rather than Holland.
Elburg was also a notable city in the region, but I'm not sure splitting Harderwijk is really necessary.
5. Roermond
The current location of Roermond is actually in Germany and fits better with the town and county of Heinsberg. Rather than completely cutting Roermond, I'd carve out a thin province for it out of the eastern parts of Weert (which were not part of the lordships of Weert and Hoorn) and tiny bits of adjacent locations. Would still be owned by Gelre (the location would also include Sittard, which was owned by Limburg and then Jullich, but that's impossible to fit)
6. Bentheim
Not technically a part of the region, but it's so close that I'm including it here (though I'll probably bring it up in the Germany map talk as well). A separate lordship thought the period and decently sized, there's really no argument against it. It even owned other locations already represented, such as Tecklenburg, Steinfurt and (probably in, just off map?) Rheda. Bentheim is famous for its sandstone (supposedly the one used for Statue of Liberty's base), so I'd obviously give it Stone as the tradegood.
Holland
The most notable change here wasn't in the locations (of which there are quite a few, mostly in Zeeland), but rather the coastline changes - there's a minor one in the north, with Wieringermeer/Hollands Kroon polder being sunk, as it was only created in the 1920s. There could be more land sank here, in the eastern parts of Alkmaar most notably, but it would make the locations uglier.
More notably, a lot of land was sunk around Zealand - the location(s) there are now actually islands, as they were throughout the period. Much of the land in the south of Rotterdam was also sunk, and Rotterdam and Dordrecht were redrawn - Rotterdam was barely in its current location and has been moved towards it, and Dordrecht was given a port it deserved.
1. Haarlem
As many people have said, Haarlem was an incredibly important city and port. It was the centre of Kennemerland, and had a population of about 10000 at the time of the Black Death - second largest in Holland after Dordrecht at the time. However it's golden age truly began with the Dutch independence, where it had a population of over 40 000 in 1622 and was a great center of arts and culture. The city had many great industries, including Textile, Beer and even Tulips - so unless Tulips are added as Johann joked before, there's quite a few options - anything from Sand to Fish to Sturdy Grains to Fiber Crops could probably work.
2. Delft
Delft is an incredibly difficult city to fit, given its proximity to both Rotterdam and Hague, but it was obviously incredibly important. A trade and university centre, one of the largest cities in Holland through the period (third in 1400 with 6500 people and second in 1560 with 14000), de facto capital of the Netherlands for a while, famed for its Delft porcelain. In addition to the porcelain, it was also famous for cloth and beer, and had peat growing areas as well, so there are again many raw good options. I even managed to sneak in coastal acces for it, given its importance to Dutch colonization, but this is not fully necessary.
3. Amersfoort
Again, many people already requested it as a way to split Utrecht (the current location is already slightly redrawn). Large and important throughout the period, it also owed its wealth to cloth and beer brewing, like much of Holland. Later it became famous for its tobacco production, but that's obviously not appropriate for a starting tradegood.
4. Culemborg/Gorinchem
Now this might be one of my more interesting ideas. This area between Holland and Betuwe had numerous small lordships - Arkel, Altona and Culemborg. Culemborg, a city since 1318, survived as a separate fiefdom outside the Netherlands until the 18th century, often serving as a legal refuge. Seems to have mostly produced Beer and Wheat. Gorinchem has also been a city since the 14th century, however it's lordship of Arkel survived far shorter, being incorporated into Holland by 1417. The city of Leerdam is also in this location and later became famous for its glass - so Sand could be used to represent this.
5. Brielle
Brielle was an old and important city and fortress, and a major trading centre, especially towards the Baltic Sea. It was the seat of the County of Voorne, separare from Holland until 1371. Brielle was owned by England between 1585 and 1616 as one of the three Cautionary towns ( and the only one that can be represented, as Vlissingen and Fort Rammekens are far to close to Middelburg). Also includes Middelharnis and Ouddorp on the nearby islands of Goeree and Overflakke - this location generally represents the islands that are a part of South Holland rather than Zeeland. Agriculturally, peat, Wheat and Livestock were all produced
6. Zierikzee
Representing the middle/northern islands of Schouwen and Duiveland, Zierikzee was the most important city on them, having had city rights since 1248 and being strategically important in numerous conflicts. Also includes Brouwershaven, the second city on Schouwen. The islands produced many things- fish, shellfish, vegetables and traded in wine and beer, but Salt was by far the most important tradegood that made Zierikzee and Brouwershaven rich
7. Goes
Goes was an important city, having city rights since 1405, though it declined later in the period. Most of its wealth came from Salt and cloth trade, making Salt the ideal tradegood
With these, Middelburg becomes a small island location, representing Walcheren and West Beveland. Vlissingen would also be nice to add given its importance, but it's far too close to Middelburg on their small island. The Middelburg location, less known for Salt than Zierikzee and Goes, can be changed to produce Fish instead.
8. Texel
I find it sad that all of the Dutch islands outside of Middleburg are here represented as part of mainland locations. This and the next one are perhaps the least historically important locations I'm suggesting, but players love islands, and they offer interesting alternative history options - say, England or Denmark seizing and island to project power and keep the Dutch in check (much like England did with Brielle, see above). The biggest and most populous, and therefore the most obvious addition is Texel, a part of West Friesland already conquered by Holland by 1337. Texel had city rights and certain autonomy, and saw numerous naval engagements nearby. Would also include Vlieland. Texel is best known for its sheep, so Wool is the ideal tradegood- through later a whaling industry developed, and naturally fishing was prominent as well.
9. Ballum
The capital of the island of Ameland, the location also includes the island of Terschelling (known by its ancient name of Wexalia, or Skylge in Frisian). These two were the most important of the Frisian Wadden islands, and were eventually conquered by Holland to be used as staging grounds for incursions into Frisia. Ameland had its own lordship under the Cammingha family. Surprisingly, the islands seem to have produced more Grain than Fish - though both work as a trade good
10. Montfoort
Added this late based on a forum sugfestion! Montfoort has been a city since 1329, but it was most prominent due to the Viscounts of Montfoort, which were powerful disloyal vassals of Utrecht until the 17th century. A mostly agricultural area before ropemaking and buttonmaking industry developed, Wheat is the best tradegood.
With these additions, Utrecht and Zeeland can both be separate provinces.
Brabant
1. Ravenstein
A small lordship just to the west of Cuijk, also including the Teutonic lordship of Gemert. The lordship of Herpen (which after its founding in 1360 became the better known Land of Ravenstein) was small, but was an enclave of other states - in 1337 it was held by the Valkenburgs of Limburg, and later for a long time by the Duchy of Cleves and Brandenburg, only becoming part of the Netherlands in the 1630s. This might be a bit too small to add, but it is certainly a worthy addition from a geopolitical standpoint
2. Tilburg/Waalwijk
While not very important at the beginning of the game, Tilburg became the centre of the Dutch Wool industry in the 17th century - it was however, already a lordship at the game's start so the name was well known and used. If you want to avoid giving a location to a less important place, Waalwijk (which became a city in 1303) also works for the location, perhaps being replaced by Tilburg later (as does Oisterwijk right next to Tilburg). The tradegood is obviously wool
3. Bergen op Zoom
It is still unclear to me whether this is already in? Seems not, so the addition is quite obvious. Breda has atrocious borders, and Bergen was a separate Lordship and a city since 1212. The city was best known for its military arsenal and armory, but of raw goods it produced and processed a lot of dyer's madder, making Dyes a good choice.
4. Lier
An important city and site of key events in Flemish history, though it was in time overshadowed by other cities in the province, partly through choices such as deciding to host a sheep market rather than an university (which was eventually founded in Leuven instead). To represent this, Wool would be a cute tradegood, but Clay also works as it may be the root of the city's name. This also reduces the size of Turhout, as well as of Mechelen, which should be a small independent lordship for much of the early period of the game.
5. Tienen
Making Leuven a smaller, more urban province akin to Brussels and representing the other cities of Brabant (including Diest and Aarschot most notably, either of which could also be its own location), Tienen would be a good addition. It was an important trade and cloth production centre, though it declined after the 15th century. Tienen is today best known for its sugar beet, but that developed only towards the end of the game period, so perhaps Sand could also work as a tradegood (as there is a sand quarry close to the city).
6. Nivelles
As noted by many people, Nivelles was more important than Wavre for most of the period, and could easily replace it - I would simply include both as locations.
Gembloux is also a possible location to add, representing the parts of modern Namur owned by Brabant in the period and a wealthy abbey, but it might be difficult to fit
Flanders
1. Sluis
As a part of the sea expansion around Zeeland, the Hulst location is practically split in two as well (which also allows for Ghent to be a coastal location). The western side should thus be a new location, with Sluis being the obvious choice, being a city since 1290 and the most important Burgundian port shortly after. This also allows for Hulst to properly be a part of the Holy Roman Empire as well. Fish seems to be a natural tradefood here.
2. Dendermonde
I felt that Land van Aalst deserves to have another location, and the most notable one is Dendermonde, a city which famously has a rivalry with Aalst dating back to the Middle Ages. It was already a city in 1233, and a major centre of the cloth industry like much of Flanders. An interesting tradegood for it could be Horses, representing the importance of the legend of Bayard to the city, though more realistically the tradegood would be Fruit, representing the apples around the city.
With these two locations, Land van Aalst can become its own province as well, given its significant separation from the rest of Flanders - theoretically a third location could be added for it, Ronse, but it isn't necessary.
3. Roeselare
Flanders is already quite dense and most of its major cities are represented, so the only further one I'd add is Roeselare, which was a powerful feudal lordship (later owned by Cleves and the Palatinate) and a city and cloth production centre since the 13th century, later also seeing great importance during industrialisation in the 19th century.
Eeklo might also be an interesting location to add, but it seems less necessary - though it did also gain a city charter early.
Walloonia
1. Enghien
A small but important location, the Dukes of Enghien held an outsized role in France later in the period - though their seat of power was close to Paris, and they were only tangentially related to the original counts of Enghien. Enghien was still a Luxembourgian and French enclave for much of the time period, and was also a wealthy tapestry weaving centre.
2. Ath
Even with Enghien split, Mons is a rather large location. Ath was a city of over 5000 people in the early 15th century and a rich trade and manufacturing centre, granted many privileges by the Counts of Hainaut who occasionally ruled from there as well. Of the things it produced, Stone is the only raw tradegood.
3. Maubeuge
Same as with Mons, Valenciennes is large and the most natural splits are Avesnes and Mauberge to the east - and while Avesnes gave its name to the county (and thus the Avesnois region) and it's powerful nobles and did have city rights and trade, Maubeuge seems like the more important settlement (with a population of about 3000 in the 13th century already!), especially later in the period where it became a massive fortress. A famous Cheese producing area, Livestock fits.
There are even more options for locations here, such as Quesnoy.
A: Chimay over Thuin
As I've seen in the France map, this already happened, so no need to argue further for it.
4. Thuin
Thuin was an important city and should be represented however, so a location should be added from the north of Walcourt/Couvin (see below) - given that you added it in the first place, I feel like there's less need for me to argue in its favour.
B: Couvin over Walcourt
Despite Walcourt being slightly bigger today, Couvin seems like a much better location to represent the southwestern parts of P-B of Liège for this time period, as it was one of its bonne-villes.
5. Orchimont
Bouillon (and St. Hubert) were actually separate from the rest of Liège's narrow band of territory by land owned by Chiny (and after it, Luxembourg). The most important town here was Orchimont until it was sacked by the French in the 17th century, but there were also other towns such as Gedinne
6. Verviers
The lands surrounding Liege were the wealthiest in modern Walloonia throughout the period, especially as they became some of the first places in continental Europe to industrialize. While it's not wrong, I'm surprised to see them represented by just one location.
That's why I'd suggest Huy and Verviers. Verviers was a large cloth manufacturing centre and later one of the first true industrial cities in Europe. Verviers (and Theux) were also the centres of the Marquessate of Franchimont, a separate lordship within the Prince-Bishopric's lands - also taking some land currently in the Limburg location and correcting the border.
7. Huy
Most of the reasoning is explained above, Huy too was a big centre of manufacturing (mostly metallurgy and cloth) and later an industrial centre, and the capital of its own county within Liège.
C: Tongeren over Maasmechelen and Masseik over Lommel
As others have pointed out, Maasmechelen is an odd choice for the location capital - I would replace it with Tongeren (oldest city in Belgium, also (alongside Sint Truiden) owned directly by Liege rather than being part of the Loon vassal) or Borgloon (gives the name to the county).
Masseik would also be a better location name than Lommel, as it was a more important city throughout the period - and indeed Lommel was not a part of the County of Loon/Liège at all, being owned by Brabant and later The Netherlands.
D: Eupen over Limburg
While Limburg may gave given its name to the province and state, for most of the game's timeline it was Eupen that was the bigger city
Luxembourg
1. Vielsalm
Vielsalm would be a nice addition as it was one of the many possessions of the House of Salm spread throughout Belgium, France and Germany - their original seat in fact. The area was notable for Stone mining
2. Diekirch/Echternach
Vianden in Luxembourg was a separate lordship (whose original lords interestingly died out in September of 1337) independent of Luxembourg, though it was rather small. Instead of Vianden itself, the location could be called Diekirch but owned by the Vianden tag, as Diekirch was a much more important town. Echternach is also in this area, and was an important pilgrimage site and the oldest city in Luxembourg, and would also be a good name for the location.
Chiny and Orchimont should be owned by the Counts of Chiny, much like Montmedy already is. Arlon is significantly redrawn to better approximate both the modern border and the border between Chimay and Luxembourg. This leaves Luxembourg somewhat large, and thus:
3. Grevenmacher
Covering eastern Luxembourg, Grevenmacher was the most important town between Luxembourg and Trier. It was, and is, most notable for its production of Wine, making that a natural tradegood.
4. Durbuy
While this would be a small location for a relatively small city, I think it is warranted - Durbuy was the centre of the County and Land of Durbuy, and was granted city privileges in 1331 - it is specifically noted that it had the same privileges as Bastogne and La Roche, the two locations represented nearby. The area is noted to be especially wealthy in the late Middle Ages due to Metallurgy, making Iron a good tradegood here.
In the next post I'll comment on the changes made and what could be further done to improve the map! Most of the regions got much better, with the only remaining significant suggestions being in Holland&Zeeland, Brabant, and around Liege and Groningen